Process of producing electrochemical products or energy from a fiberous electrochemical cell

ABSTRACT

The subject invention relates to a process for electrosynthesis of compounds or generation of electrical power utilizing a fibrous electrochemical cell comprised of at least an inner fibrous electrode, a membrane separator, a lumen for free passage of liquid or gas, electrolyte, and a second outer electrode. Liquid or gaseous feed is contacted with the electrodes which are isolated and sealed at the shell and bore side of the fibrous cell as in a shell and tube heat exchanger.

This application is a Divisional to U.S. Pat. application Ser. No.08/869,448, filed Jun. 5, 1997 pending.

BACKGROUND OF THE INVENTION

In U.S. Pat. application Ser. No. 08/549,976 a fibrous cell structurefor fabrication of batteries was disclosed. The fibrous geometry of thecells described provides an extremely high surface area to volume ratiowhen multitude of small fibers are packed into a given volume. Ingeneral, the smaller the fiber OD (outside diameter), the higher thesurface area. The high surface area available to electrodes translatesinto a higher number of active sites participating in theelectrochemical reaction, hence, giving rise to higher energy densitybatteries. This concept is true for all electrochemical cells. Forenergy producing electrochemical cells such as full cells, the highsurface area to volume ratio, similar to batteries results in higherenergy density. For electrochemical cells that produce a product, thisresults in lower energy requirement. In addition, the high surface areaavailable to the electrocatalyst reduces the requirement of the unusedbulk quantities on the electrodes, and further reduces the material andfabrication cost of the cells.

It is an object of this invention to provide a structure for fabricatingelectrochemical cells that have fibrous geometry and can be made withfibrous electrodes ranging in size between about 10 micron to about 10millimeter.

It is also an object of this invention to incorporate the fibrous cellsinto various electrochemical cell designs for fabricating batteries,fuel cells or other electrochemical reaction cells.

SUMMARY OF THE INVENTION

The subject invention relates to fibrous electrochemical cells used forconstruction of electrochemical cells such as batteries (rechargeableand non rechargeable) fuel cells, and other electrochemical reactioncells. The outside diameter of the cells range between about 20 micronto about 10 millimeter depending on the cell application or requirement.The fiber cells are fabricated as a continuous fiber, but can be cut tothe desired lengths for packaging into an electrochemical module.

In the cells of this invention, a fibrous electrode, composed of one ormore fibers ranging in size between about 10 micron to about 10millimeter is encapsulated by a membrane separator, preferably apolymeric material. The fibrous electrode and membrane separatorassembly forms the building block of a fibrous cell. In the case ofbatteries the separator can closely cover the circumference of theelectrode without a passage route in the lumen of the fiber.

For other electrochemical cells, a passage inside the lumen of theseparator fiber is allowed for transport of the reactants to and fromthe electrode, inside the membrane separator. The membrane separator hasa permeable or porous structure which can immobilize and hold theelectrolyte in the membrane matrix, or in the cavities of the porouswall of the membrane. The electrocatalyst (or the active material in thecase of batteries) with or without an electrically conductive materialis impregnated, coated or extruded on the outer pores of the membraneseparator. In this case one fiber contains the first electrode, theseparator, the electrolyte, and the electrocatalyst (or the activematerial) of the second electrode or the entire second electrode. Theelectrocatalyst of the second electrode alternatively can be coated ontoanother fibrous substrate and placed adjacent to the membrane insulatedelectrode. With this configuration two fibers will complete a singlecell.

The subject invention also relates to assembling the fiber cells into amodular form that can be used as rechargeable and non-rechargeablebatteries, fuel cells, and other electrochemical reaction cells formanufacturing various products.

DETAILED DESCRIPTION OF THE INVENTION

This invention relates to fabricating fibrous electrochemical cells andto incorporating the fibrous cells into modules for variouselectrochemical applications. In this invention a fibrous electrode isencapsulated by a layer of a membrane separator which may be impregnatedor coated with the electrocatalyst of the second electrode with orwithout an electrically conductive material. In this process cells ofvarious sizes are fabricated as a continuous fiber. With cells having anOD of about 1 millimeter or less, an extremely high surface area ofactive electrocatalyst can be packed into a given volume. The membraneseparator of the cell of this invention has a semipermeable matrix, orporous wall with small cavities ranging between about 5 Angstrom to afew microns, the pore size and structure of which can be tailored todesired specifications. The pore size and structure of the membrane issuch that it immobilizes and retains the electrolyte, allows freetransport of ions and dissolved gases from one electrode to the otherand isolates the two electrodes, preventing short circuiting. The rigidmembrane structure also, provides an structural support for impregnationand coating of the electrocatalyst of the second electrode or otherpolymers such as ion exchange resins or permselective polymers.

Fiber glass sheath material has been used in fabricating certain tubularbattery cells as a separator material. The battery cells made with fiberglass sheath material have several limitations. In general, the cellsare limited in size to the tubular structures with larger outsidediameter and shorter length. Furthermore, the fiberglass sheath does notexhibit the same structural characteristic nor the flexibility intailoring the pore size and structure of the separator, as does theseparator of the cells of this invention, for forming a barrier betweenthe liquid or gas feed introduced to the electrodes.

For electrochemical cells other than batteries, the capillary pores ofthe membrane when filled with the electrolyte, also act as a barrier forthe feed introduced or product produced on either side of theelectrodes.

In the design of the cells of this invention, the insulator or separatorwithout an electrode inside of it, has an structure similar to a hollowfiber membrane. FIG. 1A, and 1B shows the side view and cross section ofa hollow fiber membrane. Hollow fibers membranes are extremely smalltubes with an inside or outside diameter of about 30 micron to a fewmillimeter. The walls of the hollow fiber membranes are porous withpores ranging from a few angstroms to a few microns depending on thetype of membranes. Based on the size of wall pores, hollow fibermembranes are classified as micro filtration, ultra filtration, reverseosmosis, etc. The porous, open structure walls of microporous hollowfiber membranes allow free transfer of liquids or gases from the outsideor shell side of the fiber to the inside or the bore side of the fiber.In semipermeable membranes the membrane structure is denser without welldefined pores of the microporous membranes. The membranes are permeableto certain molecules through sorption and diffusion of the moleculethrough the membrane matrix. Hollow fiber membranes can be fabricatedfrom variety of polymeric material such as polypropylene, polysulfone,regenerated cellulose acetate, polyamide, polyacrylonitrile, polyethylmethacralyte to name a few and from other materials such as glass andceramics. Polymeric hollow fibers are typically fabricated by variety ofwet, dry or melt spinning techniques. The fabrication of various typesof hollow fiber membranes has been covered extensively in openliterature and is well documented. Examples of more detailed descriptionof hollow fiber membrane fabrication can be found in the journal ofSeparation Since and Technology, 27(2), pp. 161-172, 1992, and under thereference ; I. Cabasso, "Hollow Fiber Membranes", in Kirk-OthmerEncyclopedia Of Chemical Technology (M. Grayson and D. Eckroth, eds),Wiley, New York, 1980, p.492. The hollow fiber membranes and the methodof fabricating same are not the subject of this invention. However, if afibrous electrode composed of one or more fibers (or the electrocatalystof an electrode with one or more electrically conductive fibroussubstrate) is encapsulated by the membrane, the membrane can then beused as a separator for the electrodes with exceptional properties. FIG.2A shows the configuration of a membrane separator with a fibrouselectrode inside the bore. For battery cells the separator can beapplied to tightly cover the fibers with minimal or no space between theelectrode fiber and the separator. In the case of other electrochemicalcells, a passage in the lumen of the membrane separator is needed toallow transport of liquid or gaseous feed or product through the bore ofthe separator. As shown in FIG. 2B, this open passage way is introducedsimply by fabricating the separator with an ID sufficiently larger thanthe OD of the electrode fiber or by the interstitial space betweenmultiple fibers, as in FIG. 2C. Alternatively, a hollow fiber coatedwith the electrocatalyst is encapsulated by yet another membraneseparator with fibrous current collectors (suppliers) on the shell sideof the inner fiber. These configurations are the building block of afiber cell.

Many different techniques can be used to form a thin layer of a membraneinsulator or separator with porous, open structure around a fibrouselectrode or substrate. One preferred method is to imbed the fibrouselectrode inside the bore of a membrane fiber by extruding the membraneforming polymer(s) around a continuous string of a fibrous electrode.For example, as shown in FIG. 3, the membrane dope or formulation ispumped through an orifice on the extrusion mold refereed to as"spinnerette". A liquid or gas is blown through a bore-forming tube,located in the center of the extrusion orifice, as an internal coagulantor quenching media. During the spinning process, the membrane dope isextruded through the orifice opening and around the bore-former tube.The circumference of the bore-former tube forms the inside diameter ofthe hollow fiber. A string of fibrous electrode is pulled from anexternal source through the bore-former tube of the spinnerettesimultaneously as the membrane material is extruded through the orifice.The membrane structure is formed around the fibrous electrode as thecoated fiber is pulled through a quenching or a coagulation media suchas a solvent or a gas, and the polymer is solidified. The composition ofthe dope formulation depends on the type of membrane that is fabricated.In general, the formulation includes a polymer that forms the backboneof the membrane, a solvent that the membrane polymer is dissolved in, apore former compound that can be leached or extracted out of the polymermatrix. An example for fabrication of an ultrafiltration polysulfonetype membrane separator is a dope composed of 10 to 30 wt %.Polysulfone, dissolved in 60 to 70% N,N-dimethylacetamide (DMAc), and 10to 20% polyvinylpyrrolidone (PVP). In a coagulation bath of water, thewater soluble solvents leach out of the membrane solution leaving aporous polysulfone membrane around the electrode. The membrane poresize, structure, and thickness formed depends on dope composition,viscosity, temperature and pumping rate, spinning temperature,composition of the internal and external coagulant, coagulation orquenching temperature, and fiber take up rate. Some membrane separatorsmay require post treatment with plasticizing or wetting agents forretention of the membrane properties or further surface modifications.For example, the outer surface of the separator may be coated with anion exchange resin such as Nafion or other perfluorinated ionomers or apermselective polymer. The membrane wall may have a porous isotropic oranisotropic (asymmetric) morphology, meaning a highly porous structurewith foam like or channel like structure with tight surface skin. Thisfeature is important in using the membrane as structural support forimpregnating or coating with an electrocatalyst or an ion exchangepolymer. In this example, the electrocatalyst can be imbedded inside thelumen of the separator as a suspended solution or slurry along with theinternal coagulant. In that case a fibrous current collector will beused instead of an electrode. In the above example, the electrode fibersmay also be physically threaded inside the bore of a hollow fibermembrane depending on the size or length of the fiber, using vacuum orother techniques.

Another method to form a thin layer of a porous separator materialaround a fibrous electrode or substrate is the conventional dip or spraycoating of the fiber electrodes, using the polymer formulations that isused to fabricate the membranes followed by inserting into a quenchingmedia similar to above extrusion process. Using this technique, a thinlayer of the insulator material is coated on the fibrous electrodefollowed by the solidification and formation of the porous structure inthe quenching media or the coagulation bath. With the coating technique,the control over the separator thickness may not be as accurate as theextrusion process. Other coating processes such as plasma, vapordeposition or polymerization may also be used with the exception thatthe separator material used can be transformed into a porous, permeablestructure if the coating technique used does not produce an open orporous structure. A non porous insulator can be transformed into aporous, membrane like structure by other techniques such as leaching, orpunching sub micron holes into the material using lasers.

The outer walls of the membrane encapsulated electrodes of the aboveexamples are then coated or impregnated with the electrocatlyst of thesecond electrode or another polymer if required. The membraneencapsulated fibers can be impregnated by, for example, passing thefibers though a slurry made from the electrocatalyst followed byremoving the excess coating, or thinly dip coated with a slurry that maycontain a binding agent. The electrocatalyst can alternatively beextruded onto the membrane/electrode assembly using an extrusion processsimilar to the above example and as shown in FIG. 4. In the above cases,further treatment such as heating the fibers, may be required to dry orcure the electrocatalyst or the polymer coating on the fiber. The coatedelectrocatalyst may also contain an electrically conductive compound orsubsequently coated or extruded again with an electrically conductivecompound. FIG. 5 shows a fiber cell that contains an electrodeencapsulated with a membrane separator, and electrocatalyst coated onthe shell side of the separator. The electrochemical reaction and iontransport from one electrode to the other takes place on both sides ofthe porous wall of the membrane separator that may have a thickness of afew microns to a few millimeter. Electrically conductive currentcollectors (or suppliers) which are also in fibrous form can be placedalongside and parallel to the fiber cell to collect current or supplypower from and to the electrocatalyst of the second electrode on theshell side of the fiber cell, if the electrocatalyst of the electrode isnot electrically conductive or does not contain an electricallyconductive material. FIG. 6 shows the configuration of fiber cells andthe current collectors or suppliers. When the fiber cells are wound orpacked in parallel, each current collector (supplier) comes in contactwith the outside walls of the other fiber cells in its surrounding.

If the electrocatalyst of the second electrode is not coated onto theoutside wall of the membrane separator, it can be impregnated, coated orextruded on a fibrous current collector forming a second electrode.Similar to the configuration shown in FIG. 6, the second electrode willlie in contact or parallel to the membrane and the first electrodeassembly. In these configuration the first and the second electrodecould be either negative or positive electrodes.

For electrochemical cells other than batteries a cell structure mayinvolve coating the electrocatalyst on a hollow fiber membrane,encapsulating the coated fiber along with one or more of currentcollector (supplier) fibers with another membrane separator, coating theouter surface of the separator with the second electrocatalyst as shownin FIG. 7, and encapsulating again with another layer of the porousmembrane material as a protective coating with one or more currentcollector (supplier) fibers. With this cell configuration, the feed orreactants to the electrode are introduced inside the bore and to on theshell side of the cell. The multiple encapsulation structure describedabove are done using an extrusion process similar to the process shownin FIG. 3.

An advantage of the cells of the present invention is that a smallamount of the electrocatalyst can be impregnated, coated or extruded ona fibrous substrate to form an electrode. This may be done, for exampleby plasma deposition of one or few atomic layer of the electrocatalyston the fibrous electrode, resulting in lower material weight and cost.

The choice of the material of construction for the membrane may dependon the type and application of the battery, fuel or electrochemicalreaction cell. Polymeric material such as polypropylene, polysulfone,polyethylene, regenerated cellulose acetate, and any other polymerscurrently used in fabricating hollow fiber membranes including glass andceramics can be used to fabricate the separator. For example, for hightemperature fuel cells a glass or ceramic membrane separator materialmay be required. It is important to choose a material that is compatiblewith the electrolyte used, i.e., the electrolyte, the reactants,products, and intermediates would not deteriorate the separator.Membranes separators of various pore sizes can be used as the separatormaterial. In general, the smaller the pore size the higher the capillaryeffect for liquid electrolyte retention.

The fiber cells of the present invention can be packaged into containersof various sizes in parallel or series in order to make batteries, fuelcells or other electrochemical cells.

To use the fiber cells of this invention for various electrochemicalprocesses other than batteries, the fiber cells are densely packed in ahousing such that the bore side of the fibers which contain an electrodeis isolated from the shell side of the cells which contain the otherelectrode, a modular unit such as shell and tube heat exchangers units.

As an example, fiber electrodes encapsulated with the membrane separatorand fibers of a second electrode are densely bundled around a perforatedtube shown in FIG. 8A. This tube, as will be shown in the finalassembly, serves as the feed tube to the shell side of the fibers. Thefiber bundle is epoxy potted at both ends, with the fibrous substratesextending through the potted area, in order to isolate the bore andshell side of the fibers. For ceramic fibers or high temperatureapplications, ceramic potting material may be used. The potted ends arethen machined to the desired size to form a tube sheet. The ends of theelectrodes (the substrate fiber) inside the bore of the fiber cells andthe second electrodes from the shell side are connected to a commonconnector in order to form a single anode or cathode. Alternatively, anelectrically conductive strap wrapped around the bundle can form asanode or cathode if the fiber cells have sufficient electricalconductivity. The fiber bundle with "O" ring seals is inserted in ahousing with feed inlet and outlet for the shell side and the bore side.A cross sectional view of potted fiber cells and side view of the fiberbundle in the housing are shown in FIGS. 8B and 9 respectively.Alternatively, the bundle can be permanently potted in the housingsimilar to FIG. 9 without the requirement of machining or "O" ringseals. In an electrochemical process, reactants or feed, in liquid orgaseous form are contacted with the electrodes, by passing the materialthrough the bore or the shell side of the fiber cells. The fiber bundlehousing can be a polymeric or metallic material depending on thetemperature and pressure requirement of the process. The housing designfor utilization of the fiber cells is not the subject of this invention.Similar housing designs have been extensively cover ed in literature forfabrication of hollow fiber membrane separation units.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B depict cross sectional view of a hollow fiber membrane1, the bore of the separator 2, and the porous wall of the membrane 3.

FIG. 2A shows the hollow fiber membrane 1 as separator for fibrouselectrode 4.

FIG. 2B shows OD of the electrode 4 selected smaller than separator IDto allow passage 5 for liquid or gas feed or product.

FIG. 2C shows a tow of electrodes 4 creating passage 5.

FIG. 3 illustrates the process for forming a layer of membrane separatoraround a fibrous electrode. A string or a tow of electrode fibers 7 fromelectrode spool(s) 6 are passed through the bore former tube 9 of anextrusion mold (spinnerette) 8. A stream of a membrane formulation 10 ispumped from tank 12 using pump 11 to the spinnerette and through theorifice and around the bore former tube with electrodes(s) runningthough it. Gaseous, or liquid internal coagulants (with suspended slurryof electrocatalyst) 13 is pumped from tank 14 through the bore formertube 9. The extruded fibers enter a coagulation or quenching bath 15,where the bore former is extracted by the gaseous or liquid media 16.The membrane covered electrode 17 is taken up by winder 18.

FIG. 4 depicts the process flow diagram for extruding electrocatalystpaste (or a polymer) on the membrane/electrode assembly 17. The fiber 17is passed through the bore former tube 9 of the spinnerette 8.Electrocatalyst paste (or coating polymer) is pumped from tank 20 usingpump 19 around fiber 17. The coated fiber cell 22 is cured and driedwith heat panels 21.

FIG. 5 illustrates the cross sectional view of fiber cell 22. Electrode4 is surrounded by membrane 3. Electrocatalyst 23 is impregnated, coatedor extruded onto the membrane wall.

FIG. 6 depicts cross sectional view of fiber cells 22 packed withcurrent collectors (suppliers) 24.

FIG. 7 shows alternative cell design for liquid or gaseous passage. Aninner hollow fiber membrane 1 is covered with electrocatalyst material23. Electrodes 4 or current collector (supplier) 24 are placed inintimate contact with the shell side of inner membrane. A layer ofmembrane separator 3 is extruded onto the inner hollow fiber andelectrode(s). A layer of eletrocatalyst 23 is extruded on the wall ofthe outer membrane.

FIG. 8A shows mandrel tube 25 with a perforated mid section.

FIG. 8B shows the cross sectional view of potted end of a tubesheetcontaining mandrel 25, fiber cells 22, and current collectors (supplier)24 , potting matrix 26, and optional "O" ring 27.

FIG. 9 illustrates side view of an electrochemical cell module 28. Fiberbundle 29 is placed inside casing 38 with mandrel 25 extending throughthe casing. The tubesheet 26 is sealed to the casing by "O" rings 27.The positive or negative electrodes 31, and 32 are connected to plates33 and 34 to form the positive and negative terminals. Casing 38 canoptionally have a flanged cap 30 at one end to allow insertion of thefiber bundle 29 inside the casing. Casing 38 has inlet and outlet 36 and37 to the lumen side of the cells and inlet and outlet 25, and 39 to theshell side of the cells. Plates 33 and 34 are electrically connected toan outside source as cathode or anode 40, and 41. Alternatively, anelectrically conductive strip 35 can be wrapped around the bundle toform a positive or negative terminal if the shell side of cells havesufficient electrical conductivity.

FIG. 10 shows the side view of a battery cell. Fiber cells 22 are packedin parallel. Electrodes 4 and current collectors 24 are connected toplates 33 and 34 to form positive or negative terminals.

FIG. 11 shows an electrochemical cell module 28 as a fuel cell. Oxygen42, and hydrogen 43 are introduced to the bore side and the shell sideof the fiber cells. Back pressure regulators 44 and 45 control thetransmembrane pressure.

FIG. 12 illustrates an electrochemical cell module as a chloro-alkalicell. Concentrated NaCl solution 47 and water 46 are introduced to thebore and shell side of the module 28. Electric current is appliedthrough terminals 40 and 41. The stream of Chlorine gas and dilutedNaCl, 53, is sent to gas/liquid separator 54 where Cl₂ gas 49 and sodiumchloride solution 48 are separated. The stream from bore side, 52, isalso sent to gas liquid separator 55 where H₂ gas 51 and concentratedNaOH solution 50 is recovered.

EXAMPLES

The following example demonstrates the application of a high surfacearea electrode for fabrication of an energy storage device or anelectrochemical cell.

Example 1 - High Surface Area Electrode

A tow of 20 fibrous electrodes (anode) with an OD of 500 micrometer wasencapsulated with a polysulfone ultrafiltration type microporousmembrane separator with a thickness of about 100 micrometer. The outsidediameter of the encapsulated bundle is about 3 millimeter. Another towof 20 electrodes was encapsulated with the same membrane as cathode.

The two electrodes are used to fabricate an energy storage device suchas a battery, or an electrochemical cell.

The following example demonstrate the extremely high electrode surfacearea that can be packed into a given volume using the fiber cellgeometry of this invention for fabricating batteries.

Example 2 - Battery Cell

The following calculation shows the electrode surface area that can bepacked into a battery container 1 cm in diameter, and 5 cm long usingfiber cells of this invention with an outside diameter of 500 micrometerplaced in parallel as shown in FIG. 10. The diameter of the secondelectrode or the current collector of the second electrode is chosensuch that it falls inside the interstitial space created by four or lessfiber cells as shown in FIG. 6.

Cross sectional area of the battery M=×(1)2/4=0.7853 cm2.

Cross sectional area of one fiber cell M=×(0.05)2/4=0.00196 cm2.

Minimum or effective surface area of the battery cross section utilizedby the fibers=78% of the total surface area=0.78×0.7853=0.6123 cm2.

Number of fibers that can be packed in the effective cross sectionalarea of the battery=0.6123/0.00196=312.

The outside or shell surface area of a fiber cell 5 cm long=×0.05×5=0.7853 cm2.

Theoretical surface area of the 312 fiber cells packed in thebattery=312×0.7853=245 cm2.

Assuming a minimum of 75% packing efficiency;

The practical surface area of the cells packed in thebattery=0.75×245=183.75 cm2.

Surface area to volume ratio: 30 cm2/cm3.

Example 3 - Battery cell

First, the positive electrode of a lead-acid battery was made by passinga lead coated metal fiber with an OD of about 200 micrometer through asolution of sulfuric acid. The wetted fiber was then coated with a thinlayer of lead, and lead oxide powder by passing it through the powdertray. The fiber was then passed over an open flame to further oxidizethe lead and fuse the powder to the fiber. The electrode was thenencased by an ultrafiltration type membrane of about 800 micrometer OD.A six inch section of the assembly of the electrode and the membraneseparator was then immersed in the sulfuric acid solution for a fewminutes to saturate the fiber pores with the electrolyte. Theelectrode/separator assembly was then coated with the lead powders by asweeping action on the powder tray. The excess powder was wiped off fromthe membrane surface leaving only a small amount of the materialimpregnated inside the surface pores. The OD of the fiber did not changeafter impregnation.

A second metal fiber, with similar dimensions was dipped into sulfuricacid and placed in parallel alongside and in contact with the cellassembly, as current collector (negative electrode), by covering the twofibers with a plastic tube of about 2 millimeter ID. Using a voltmeter,a maximum voltage of 0.90 V, and current of 0.45 A was measured.

Example 4 - Fuel Cell

Platinum coated metal fibers of approximately 200 micron OD, areencapsulated by an ultrafiltration type membrane separator of about 500micron ID. The fibers are then cut to 30 inches long. Cathode Electrodesof the same size are bundled alternatively with the membrane coveredelectrodes. The bundle, containing approximately 83 square feet surfacearea, is epoxy potted at the ends and placed in the housing similar toFIG. 9. The housing is cylindrical with an ID of about 5 inches and is 3feet long. The effective length of the fiber cells after potting is 2feet. Water is pumped through the bore and shell side of the fibers andimmobilized as electrolyte in the porous wall of the membrane separator.Excess water is drained out of the fiber cell module. The module is thenconnected to hydrogen and oxygen gas tanks as shown in FIG. 11. Thepressure on either side of the fiber cell is controlled and balanced bypressure regulators if required. The cell module exhibits the followingfeatures:

Surface area to volume ratio of about: 244 ft2/ft3

Module is run at a transmembrane pressure with water remainingimmobilized in the membrane pores due to the capillary effect.

Water can be circulated through the membrane under high pressure toprevent drying on anode side.

Module can be operated under high gas pressures.

Example 5 - Chlorine production

A fiber cell module similar to Example 2 is used as a chloro-alkali cellwith the exception that the membrane separator is coated with Nafionsolution and electrodes contain Ruthenium and Iridium electrocatalyst. Aconcentrated NaCl solution is pumped through the bore of the fiberswhile pure water is pumped to the shell side. A voltage is maintainedbetween the anode and the cathode. Chlorine gas and diluted NaCl fromthe cathode are sent to a gas/liquid separation drum in which theproduct gas is recovered. Similarly, the hydrogen and concentrated NaOHare recovered from the anode. The process flow diagram is shown in FIG.12. The cell Module exhibits the following features:

High surface area

Low operating voltage due to virtually no spacing between the membraneand the electrodes.

Low electrocatalyst cost due to high surface area utilization.

What is claimed is:
 1. An electrochemical process for generatingelectrical energy or chemical products comprising the passing of agaseous or liquid feed through fibrous electrochemical cells of anelectrochemical module, said cells comprising, at least one hollow,fibrous, porous, membrane separator having a bore side, shell side andlumen, an electrolyte disposed in the pores of the separator, at leastone inner electrode located within said lumen of said bore side and atleast one outer electrode located adjacent to the shell side of saidseparator, said electrodes formed from electrically conductive fibers incontact or covered with an electrocatalyst, forming positive andnegative electrodes, and at least one feed inlet and outlet from saidelectrodes, where said feed is passed from the shell side or through thelumen of the bore side of said membrane separator, said feed contactingthe positive and negative electrodes of a fibrous electrochemicalcell;placing said electrochemical cells in a casing, sealing andisolating said shell or bore side of said electrochemical fibers,connecting said electrodes to plates forming positive and negativeterminals, and reacting said feed components on said electrodesgenerating electrical energy or applying a voltage to said terminalsgenerating chemical products.
 2. The process of claim 1 wherein saidinner electrode is formed from an electrically conductive fiber coatedwith an electrocatalyst.
 3. The process of claim 1 wherein said innerelectrode is formed by coating or impregnating an electrocatalystmaterial on the shell side of a second, inner, porous, hollow fiberwhich has at least one fibrous current collector in contact with theshell side of said second, inner porous, hollow fiber forming an innerelectrode; said inner electrode housed within the bore of the firsthollow, fibrous, porous membrane separator, wherein the lumen of saidsecond, inner, porous, hollow fiber allows for free passage of feedcomponents to said inner electrode.
 4. The process of claim 1 whereinsaid inner electrode is formed from an electrically conductive fibercoated with an electrocatalyst, said coated fiber in contact with theshell side of a second, inner, porous, hollow fiber forming an innerelectrode; said inner electrode housed within the bore of said firsthollow, fibrous, porous membrane separator, wherein the lumen of saidsecond, inner, porous, hollow fiber allows for free passage of feedcomponents to said inner electrode.
 5. The process of claim 1 where saidouter electrode is formed from coating or impregnating anelectrocatalyst material on the shell side of said hollow, fibrous,porous membrane separator, or by placing an electrically conductivefiber coated with an electrocatalyst in contact with the shell side ofsaid hollow, fibrous, porous membrane separator.
 6. The process of claim1 where said electrochemical cells have an outer diameter from about 100micrometers to about 10 millimeters.
 7. The process of claim 1 where atleast one electrode is composed of one or more fibers having an outerdiameter from about 10 micrometers to about 10 millimeters.
 8. Theprocess of claim 1 where said feed components to said electrodescomprise hydrogen and oxygen.
 9. The process of claim 1 where at leastone feed component is a sodium chloride solution.
 10. The process ofclaim 1 where at least one feed component is circulated through theshell or pore side of the electrochemical cell.
 11. The process of claim1 wherein the porous, membrane separator is selected frommicrofiltration, ultrafiltration, reverse osmosis, semi-permeable, orion-exchange membranes.
 12. The process of claim 1 wherein the porous,membrane separator is fabricated from a material selected from the groupconsisting of ceramic, glass and polymeric membranes.
 13. The process ofclaim 1 wherein the porous, membrane separator further comprises aperm-selective or ion exchange polymer coated onto the shell or boreside of said separator.
 14. The process of claim 1 comprising applying atransmembrane pressure across the shell or bore side of said membraneseparator.
 15. The process of claim 8 comprising circulating water vaporor water liquid through said shell or bore side of said electrochemicalcell.